Cops yesterday arrested the homeless man accused of fatally pushing a college student onto the L-train tracks in Williamsburg, authorities said .
Officers spotted Ryan Beauchamp, 33, on Bushwick Avenue near Scoles Street at around 2 p.m. and whisked him away to the 94th Precient station house for questioning.
Beauchamp was allegedly boozed up late Friday night when he began hassling passengers — including La Guardia Community College student Joshua Basin — on an eastbound L train.
When the train pulled into the Bedford Avenue station, Beauchamp allegedly attacked Basin, 20, on the platform before they both fell onto the tracks as a Manhattan-bound train rolled in.
Beauchamp climbed up from the tracks, but Basin didn’t make it up in time.